In order to develop the aroma and flavor of the green coffee bean, the coffee must be roasted. Over the years various techniques of roasting coffee to improve the flavor, the extractability and the aroma have been developed. These include both batch processes where coffee is roasted in portions and then cooled or quenched, as well as continuous roasting processes where coffee is continuously fed to a roaster and cooling unit.
To achieve proper color development, the roasting process must be carefully controlled. Green coffee must be heated to a temperature above 300.degree. F. (149.degree. C.) for roasting to occur. In typical commercial processes the green coffee is roasted to a temperature from about 400.degree. F. (204.degree. C.) to about 450.degree. F. (232.degree. C.) in a period of 3 to 15 minutes. The length of time the coffee is heated affects the product density, moisture content and extractability. A fast-roasted coffee, i.e. roasted in less than 5 minutes, is generally less dense than longer roasted beans because the cell structure of the bean is expanded to a greater degree. Fast-roasted coffees also generally provide a larger yield of brew solids, i.e. they are more extractable than coffee which is roasted more slowly. This is because the greater expansion of the coffee bean cell structure renders the internal coffee bean cell walls more porous, thus allowing easier entry of brewing water into the cells and easier egress of the dissolved brew solids out of the cells.
One technique of fast-roasting coffee has been fluidized bed roasting wherein the coffee can be roasted at times of from about 30 seconds to 3 minutes. Canadian Patent No. 989,246, issued to Bergeron & Schlichter (1976) describes a coffee which has been air fluidized bed roasted in from 30 seconds to 3 minutes. The coffee beans are roasted at a bed temperature of 550.degree. to 650.degree. F. (288.degree. to 343.degree. C.) and air cooled. The coffee is then flaked to a thickness of 5 to 30 mils. This coffee was used for single serving brewing in a packet such as a tea bag.
U.S. Pat. No. 4,169,164 issued to Hubbard et al. (1979), and U.S. Pat. No. 4,322,447 issued to Hubbard (1982) describe processes for roasting coffee in a fluidized bed roaster having 2-stages. In the '164 patent the coffee is partially roasted at 440.degree. to 470.degree. F. (227.degree. to 243.degree. C.) and then finished roasted at 515.degree. to 545.degree. F. (268.degree. to 285.degree. C.), to a dark brown color. In the '447 patent the beans are roasted at the same temperature in both stages, about 550.degree. to 570.degree. F. (288.degree. to 299.degree. C.). The beans are cooled to form a low density roasted coffee having high soluble yields. The roasting time is 3 to 4 minutes. Both of these coffees are said to have increased extractability or higher yield of brew solids.
With the advent of the automatic drip coffee maker, coffee is often held in both the home and the office on a warming plate for extended periods of time. During this holding time the coffee develops bitter off-flavors and burnt notes. This is partially due to the evaporation of the water and of volatile coffee aroma components during the long heating time, and also to chemical reactions between the brew components which occur during this prolonged heating. The discovery of a roast and ground coffee which would provide a brew which could be held for extended periods of time without a significant change in flavor is highly desirable.
Surprisingly, it has been found that such a product can be prepared. The product is characterized by higher levels of sucrose, a higher ratio of 3-caffeoylquinic acid to caffeine, increased dry headspace aroma, increased extractability of the brew solids, and a lower ratio of quinic acid to 3-caffeoylquinic acid when compared to conventionally processed coffee. The brew obtained from this product is characterized by lower total acid levels, and more low molecular weight compounds in the brew solubles than conventional coffee brews. This unique coffee is prepared by processing a single grade or blend of grades of green coffee beans or green decaffeinated coffee beans under very carefully defined roasting, quenching and grinding conditions which results in less flavor degradation or volatilization.
It is an object therefore of this invention to provide a coffee product which upon brewing is less bitter and has better holding quality or freshness retention than conventionally prepared coffees.
It is a further object of this invention to provide a novel, ultrafast roasting process for the preparation of this coffee.
These and other objects of this invention will become obvious from the description herein.